Fixed diff task combined with skipSql

Do not compare modified or renamed tables with skipSql option.
Added unit test for modified table case

Added unit test for modified table case and removed check in renamed
table case due to the impossibility because of previous two checks
Merge pull request #762 from javer/patch-diff-skipsql

Fixed diff task combined with skipSql
fix DebugPDOStatement for usage with execute
Merge pull request #770 from jmglsn/master

DebugPDOStatement on execute()
reworked approach for better handling of executed queries in DebugPDO
Merge pull request #775 from thedave80/DebugPDO-fix

DebugPDO executedQueryString - quoting